Convert.ToDouble Method (String, IFormatProvider)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Converts the specified String representation of a number to an equivalent double-precision floating point number using the specified culture-specific formatting information.
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Shared Function ToDouble ( _ value As String, _ provider As IFormatProvider _ ) As Double
Parameters
- value
- Type: System.String
A String containing a number to convert.
- provider
- Type: System.IFormatProvider
An IFormatProvider interface implementation that supplies culture-specific formatting information.
Return Value
Type: System.DoubleA double-precision floating point number equivalent to the value of value.
-or-
Zero if value is Nothing.
| Exception | Condition |
|---|---|
| FormatException | value is not a number in a valid format. |
| OverflowException | value represents a number less than MinValue or greater than MaxValue. |
The return value is the result of invoking the Double.Parse method on value.
provider is an IFormatProvider instance that obtains a NumberFormatInfo object. The NumberFormatInfo object provides culture-specific information about the format of value. If provider is Nothing, the NumberFormatInfo for the current culture is used.
If you prefer not to handle an exception if the conversion fails, you can call the Double.TryParse method instead. It returns a Boolean value that indicates whether the conversion succeeded or failed.
The following code example converts String representations of Double values with the ToDouble method, using an IFormatProvider object.
' Example of the Convert.ToDouble( String ) and ' Convert.ToDouble( String, IFormatProvider ) methods. Imports System.Globalization Module Example Dim formatter As String = "{0,-22}{1,-20}{2}" ' Get the exception type name; remove the namespace prefix. Function GetExceptionType(ByVal ex As Exception) As String Dim exceptionType As String = ex.GetType().ToString() GetExceptionType = exceptionType.Substring( _ exceptionType.LastIndexOf("."c) + 1) End Function Sub ConvertToDouble(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal numericStr As String, _ ByVal provider As IFormatProvider) Dim defaultValue As Object Dim providerValue As Object ' Convert numericStr to Double without a format provider. Try defaultValue = Convert.ToDouble(numericStr) Catch ex As Exception defaultValue = GetExceptionType(ex) End Try ' Convert numericStr to Double with a format provider. Try providerValue = Convert.ToDouble(numericStr, provider) Catch ex As Exception providerValue = GetExceptionType(ex) End Try outputBlock.Text &= String.Format(formatter, numericStr, _ defaultValue, providerValue) & vbCrLf End Sub Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) ' Create a NumberFormatInfo object and set several of its ' properties that apply to numbers. Dim provider As NumberFormatInfo = New NumberFormatInfo() provider.NumberDecimalSeparator = "," provider.NumberGroupSeparator = "." provider.NumberGroupSizes = New Integer() {3} outputBlock.Text &= String.Format("This example of" & vbCrLf & _ " Convert.ToDouble( String ) and " & vbCrLf & _ " Convert.ToDouble( String, IFormatProvider ) " & _ vbCrLf & "generates the " & _ "following output when run in the [{0}] culture.", _ CultureInfo.CurrentCulture.Name) & vbCrLf outputBlock.Text &= String.Format(vbCrLf & _ "Several strings are converted to Double values, " & _ "using " & vbCrLf & "default formatting " & _ "and a NumberFormatInfo object." & vbCrLf) & vbCrLf outputBlock.Text &= String.Format(formatter, "String to convert", _ "Default/exception", "Provider/exception") & vbCrLf outputBlock.Text &= String.Format(formatter, "-----------------", _ "-----------------", "------------------") & vbCrLf ' Convert strings, with and without an IFormatProvider. ConvertToDouble(outputBlock, "123456789", provider) ConvertToDouble(outputBlock, "12345.6789", provider) ConvertToDouble(outputBlock, "12345,6789", provider) ConvertToDouble(outputBlock, "123,456.789", provider) ConvertToDouble(outputBlock, "123.456,789", provider) ConvertToDouble(outputBlock, "123,456,789.0123", provider) ConvertToDouble(outputBlock, "123.456.789,0123", provider) End Sub End Module ' This example of ' Convert.ToDouble( String ) and ' Convert.ToDouble( String, IFormatProvider ) ' generates the following output when run in the [en-US] culture. ' ' Several strings are converted to Double values, using ' default formatting and a NumberFormatInfo object. ' ' String to convert Default/exception Provider/exception ' ----------------- ----------------- ------------------ ' 123456789 123456789 123456789 ' 12345.6789 12345.6789 123456789 ' 12345,6789 123456789 12345.6789 ' 123,456.789 123456.789 FormatException ' 123.456,789 FormatException 123456.789 ' 123,456,789.0123 123456789.0123 FormatException ' 123.456.789,0123 FormatException 123456789.0123